ROOT RESPONSES OF THREE GRAMINEAE SPECIES TO SOIL ACIDITY IN AN OXISOL AND AN ULTISOL

Sorghum roots were highly sensitive to soil solution Al present in acid Ultisols and Oxisols. Corn roots were moderately sensitive and stargrass roots were tolerant. Representative acid soils from the humid region of Puerto Rico contained less soil solution Al than did several selected from the southeastern United States at the same pH level. This confirms the observation that critical soil pH range tends to be lower in soils of Puerto Rico than in those of the southeastern United States. Soil solution Al concentration can be calculated satisfactorily from soil pH and EC of the saturated paste extract using an equation developed from the data presented.